fix(ngModel): remove reference to parentForm from removed control

This fixes cases where the control gets removed, but the control's
element stays in the DOM.
Previously, if the removed control's validity changed, a reference to
it would again be stored on its former parent form.

Fixes #12263

Author: Narretz

src/ng/directive/form.js

@@ -168,6 +168,7 @@ function FormController(element, attrs, $scope, $animate, $interpolate) {
     });
 
     arrayRemove(controls, control);
+    control.$$parentForm = nullFormCtrl;
   };
 
 

test/ng/directive/formSpec.js

@@ -58,6 +58,43 @@ describe('form', function() {
     expect(form.alias).toBeUndefined();
   });
 
+
+  it('should ignore changes in manually removed controls', function() {
+    doc = $compile(
+      '<form name="myForm">' +
+        '<input name="control" ng-maxlength="1" ng-model="value" store-model-ctrl/>' +
+      '</form>')(scope);
+
+    var form = scope.myForm;
+
+    var input = doc.find('input').eq(0);
+    var inputController = input.controller('ngModel');
+
+    changeInputValue(input, 'ab');
+    scope.$apply();
+
+    expect(form.$error.maxlength).toBeTruthy();
+    expect(form.$dirty).toBe(true);
+    expect(form.$error.maxlength[0].$name).toBe('control');
+
+    // remove control
+    form.$removeControl(form.control);
+    expect(form.control).toBeUndefined();
+    expect(form.$error.maxlength).toBeFalsy();
+
+    inputController.$setPristine();
+    expect(form.$dirty).toBe(true);
+
+    form.$setPristine();
+
+    changeInputValue(input, 'abc');
+    scope.$apply();
+
+    expect(form.$error.maxlength).toBeFalsy();
+    expect(form.$dirty).toBe(false);
+  });
+
+
   it('should remove scope reference when form with no parent form is removed from the DOM', function() {
     var formController;
     scope.ctrl = {};